But I found this online: "The best conductor of electricity is silver, though gold is used more often because it does not oxidize. But of course, copper, silver, and gold are all very close in conductivity. The best conductor of heat is Helium (in its Helium II liquid state), which can conduct heat better than diamond or silver.

It should be noted that at temperatures approaching absolute zero the metal lead becomes a superconductor, giving zero resistance to the flow of electricity."